Our long-term research goal is to enhance the value of the Patient Reported Outcomes Measurement Information System (PROMIS) in clinical research in children. To bring the work of the first phase PROMIS pediatric item bank creation to fruition will entail demonstrating superior reliability, validity, and sensitivity to change of the PROMIS measures when compared to legacy items. Our objective is to demonstrate the content and construct validity of the PROMIS pediatric tool in important medical conditions of childhood that impair physical function and result in reduced health related quality of life (HRQOL): juvenile idiopathic arthritis (JIA), cerebral palsy (CP), and pediatric chronic pain syndromes. The PROMIS pediatric pain domain is recognized to need further development to add measurement of other facets of the pain experience to the current measure of pain impact. Given the centrality of pain to HRQOL, an important driver of this proposal is to enrich the PROMIS pediatric tool by developing and testing new pediatric pain item banks to address the large unmet need for adequate measurement of pain in children. Our Specific Aims are thus: 1) to evaluate the validity and responsiveness of the PROMIS pediatric item banks with longitudinal assessments in children with JIA, CP, and chronic musculoskeletal pain. In each study population, we will assess content validity with key informant interviews, and analyze construct validity with co-administration of legacy scales and by test of responsiveness to change. A final product will be the determination of minimal important differences (MIDs) in PROMIS measures. And 2), to enhance PROMIS pediatric pain assessment with new item bank creation and testing. In recognition of the multiple facets of the pain experience, PROMIS pediatric pain items will be developed in the areas of pain intensity, pain quality, and pain behavior. Item creation will follow the established PROMIS process including qualitative item review and cognitive interviews with patients with chronic and recurrent painful conditions. Construct validity will be assessed by correlation with co-administered legacy scales. The expected outcome of the project is to foster use of PROMIS for improved PRO measurement in Pediatric Pain, Rheumatology and Rehabilitation Research.